AVIA-1065 Week 3 Day 1 PDF - Reciprocating Engines

RECIPROCATING ENGINE Intro 1 Fuel-Injection Systems AVIA-1065 2  Fuel-Injection Systems have many advantages over a conventional carburetor system:...

RECIPROCATING ENGINE Intro 1 Fuel-Injection Systems AVIA-1065 2  Fuel-Injection Systems have many advantages over a conventional carburetor system: less danger of induction system icing since the drop in temperature due to fuel vaporization takes place in or near the cylinder improved acceleration-positive action of the injection system improved fuel distribution-this reduces the overheating of individual cylinders often caused by variation in mixture due to uneven distribution better fuel economy than a system in which the mixture to most cylinders must be richer than necessary so that the cylinder with the leanest mixture operates properly Fuel-Injection Systems 3 Fuel-Injection Systems Fuel-Injection Systems vary in their details of construction, arrangement and Operation the Bendix and Continental fuel-injection systems are discussed in this section to provide an understanding of the operating principles involved 4 Bendix/Precision Fuel- AVIA-1065 Injection System 5 Bendix/Precision Fuel- consists of: – an injector Injection System – a flow divider – fuel discharge nozzles It is a continuous-flow system – measures engine air consumption – uses airflow forces to control fuel flow to the engine the fuel distribution system to the individual cylinders is obtained by the use of: – a fuel flow divider – air bleed nozzles 6 Bendix/Precision Fuel-Injection System Fuel Injector the assembly consists of: – an airflow section – a regulator section – a fuel metering section some are equipped with an automatic mixture control unit 7 Bendix/Precision Fuel- Injection System Airflow Section airflow consumption of the engine is measured by sensing: impact pressure venturi throat pressure in the throttle body – movement of the throttle valve causes a change in engine air consumption – this results in a change in the air velocity in the venturi – the pressure on the left of the diaphragm is lowered due to the drop in pressure at the venturi throat 8 9 Bendix/Precision Fuel- Injection System Airflow Section when airflow through the engine increases the diaphragm moves to the left opening the ball valve contributing to this force is the impact pressure that is picked up by the impact tubes [Figure 2-32] 10 Bendix/Precision Fuel- Injection System Airflow Section this pressure differential is referred to as the “air metering force” accomplished by channeling the impact and venturi suction pressures to opposite sides of a diaphragm 11  Airflow Section a cutaway view of the airflow measuring section is shown in Figure 2-30 Bendix/Precision Fuel- Injection System 12  Regulator Section consists of: a fuel diaphragm opposes the air metering force fuel inlet pressure is applied to one side metered fuel pressure is applied to the other side the differential pressure across the fuel diaphragm is called the “fuel metering force” the fuel pressure shown on the ball side of the fuel diaphragm is the pressure after the fuel has passed through the fuel strainer and the manual mixture control rotary plate and is referred to as metered fuel pressure fuel inlet pressure is applied to the opposite side of the fuel diaphragm Bendix/Precision Fuel- Injection System 13 Bendix/Precision Fuel- Regulator Section Injection System a ball valve is attached to the fuel diaphragm controls the orifice opening and fuel flow through the forces placed on it [Figure 2-33] the distance it opens is determined by the difference between the pressures acting on the diaphragms this difference in pressure is proportional to the airflow through the injector 14 Bendix/Precision Fuel- Regulator Section Injection System the volume of airflow determines the rate of fuel flow the difference in pressure created by the venturi is insufficient to accomplish consistent regulation of the fuel under low power settings a constant-head idle spring is incorporated to provide a constant fuel differential pressure this allows an adequate fuel flow in the idle range 15 Bendix/Precision Fuel- Injection System Fuel Metering Section attached to the air metering section contains: an inlet fuel strainer a manual mixture control valve an idle valve is connected to the throttle valve by means of an external adjustable link the main metering jet [Figure 2-34] a power enrichment jet in some injector models 16  Fuel Metering Section an idle valve [Figure 2-34] Bendix/Precision Fuel- Injection System 17 Bendix/Precision Fuel- Injection System Fuel Metering Section the manual mixture control valve produces full rich condition when the lever is against the rich stop progressively leaner mixture as the lever is moved toward idle cutoff may be adjusted externally to meet individual engine requirements 18 19 20 Bendix/Precision Fuel- Injection System Fuel Metering Section purpose: to meter and control 21 the fuel flow to the flow divider [Figure 2-35] Fuel-Injection Systems Fuel-Injection Systems vary in their details of construction, arrangement and Operation the Bendix and Continental fuel-injection systems are discussed in this section to provide an understanding of the operating principles involved 22  Flow Divider The metered fuel is delivered from the fuel control unit to a pressurized flow Bendix/Precision Fuel- divider. This unit keeps metered fuel under pressure, divides fuel to the various cylinders at all engine speeds, and shuts off the individual nozzle lines Injection System when the control is placed in idle cutoff. http://www.precisionairmotive.com/Publications/15-812_b.pdf 23 Reciprocating Engines BREAK! RETURN AT 1 24 Bendix/Precision Fuel- Flow Divider Injection System Referring to the diagram in Figure 2-36, metered fuel pressure enters the flow divider through a channel that permits fuel to pass through the inside diameter of the flow divider needle. At idle speed, the fuel pressure from the regulator must build up to overcome the spring force applied to the diaphragm and valve assembly. This moves the valve upward until fuel can pass out through the annulus of the valve to the fuel nozzle 25 Bendix/Precision Fuel- Flow Divider [Figure 2-37] Since the regulator meters and delivers a Injection System fixed amount of fuel to the flow divider, the valve opens only as far as necessary to pass this amount to the nozzles. At idle, the opening required is very small; the fuel for the individual cylinders is divided at idle by the flow divider. As fuel flow through the regulator is increased above idle requirements, fuel pressure builds up in the nozzle lines. This pressure fully opens the flow divider valve, and fuel distribution to the engine 26 becomes a function of the discharge nozzles  Flow Divider A fuel pressure gauge, calibrated in pounds per hour fuel flow, can be used as Bendix/Precision Fuel- a fuel flow meter with the Bendix RSA injection system. This gauge is connected to the flow divider and senses the pressure being applied to the Injection System discharge nozzle This pressure is in direct proportion to the fuel flow and indicates the engine power output and fuel consumption 27 Bendix/Precision Fuel-Injection System Flow Divider 28 Bendix/Precision Fuel- Injection System Fuel Discharge Nozzles air bleed configuration one nozzle for each cylinder located in the cylinder head [Figure 2-38] 29 Bendix/Precision Fuel- Injection System Fuel Discharge Nozzles air bleed configuration 30 Bendix/Precision Fuel- Fuel Discharge Nozzles Injection System air bleed configuration one nozzle for each cylinder located in the cylinder head outlet is directed into the intake port incorporates a calibrated jet 31 jet size is determined by the available fuel inlet pressure and the maximum fuel flow required by the engine fuel is discharged through this jet into an ambient air pressure chamber within the nozzle assembly Bendix/Precision Fuel- Injection System Fuel Discharge Nozzles 32 Bendix/Precision Fuel- Injection System Fuel Discharge Nozzles before entering the individual intake valve chambers fuel is mixed with air to aid in atomizing the fuel fuel pressure, before the individual nozzles, is in direct proportion to fuel flow a simple pressure gauge can be calibrated in fuel flow in gallons per hour or lbs per hour and be employed as a flowmeter Engines modified with turbosuperchargers must use shrouded nozzles By the use of an air manifold, these nozzles are vented to the injector air inlet pressure. 33 Bendix/Precision Fuel- Injection System 34 Bendix/Precision Fuel- Flow Divider Injection System Referring to the diagram in Figure 2-36 35  Flow Divider [Figure 2-37] Bendix/Precision Fuel- Injection System 36  Flow Divider [Figure 2-37] Bendix/Precision Fuel- Injection System 37 Bendix/Precision Fuel-Injection System Bendix/Precision Fuel-Injection System 39 Continental/TCM Fuel- Injection System AVIA-1065 40 Continental/TCM Fuel-Injection System Continental/TCM Fuel-Injection System injects fuel into the intake valve port in each cylinder head [Figure 2-39]  Animated Rotary Vane Pump Continental TSIO-360 Video links Continental Fuel Injection engine start Actual Rotary Vane Pump Video Links https://www.youtube.com/watch?v=tO0TUqpc1JE 43 Continental/TCM Fuel-Injection System Continental/TCM Fuel-Injection System consists of: a fuel injector pump a fuel control unit a fuel manifold a fuel discharge nozzle is a continuous-flow system controls fuel flow to match engine airflow permits the use of a rotary vane pump does not require timing to the engine  Fuel-Injection Pump a positive- displacement,(dynamic displacement pump that uses a mechanism to trap a fixed amount of fluid and then move it through the pump) rotary- vane type with a splined shaft for connection to the accessory drive system of the engine [Figure 2-40] Continental/TCM Fuel- Injection System 45  Fuel-Injection Pump a spring-loaded, diaphragm-type relief valve is provided the relief valve diaphragm chamber is vented to atmospheric pressure a check valve is also provided boost pump pressure to the system can bypass the engine- driven pump for starting this feature also suppresses vapor formation under high ambient temperatures of the fuel, and permits use of the auxiliary pump as a source of fuel pressure in the event of Continental/TCM Fuel- engine driven pump failure Injection System 46 Continental/TCM Fuel- Fuel-Injection Pump Injection System the use of an engine driven fuel pump means changes in engine speed affect total pump flow proportionally since the pump provides greater capacity than is required by the engine, a recirculation path is required by arranging a calibrated orifice and relief valve in this path, the pump delivery pressure is also maintained in proportion to engine speed these provisions assure proper pump pressure and fuel delivery for all engine operating speeds 47  Fuel-Injection Pump the process: fuel enters at the swirl well of the vapor separator vapor is separated by a swirling motion so that only liquid fuel is delivered to the pump the vapor is drawn from the top center of the swirl well by a small pressure jet of fuel it is then directed into the vapor return line this line carries the vapor Continental/TCM Fuel- back to the fuel tank Injection System 48 Continental/TCM Fuel- Fuel/Air Control Unit function: Injection System controls engine air intake to control and to set the metered fuel pressure for proper fuel/air ratio air throttle mounted at the manifold inlet and its butterfly valve positioned by the throttle control in the aircraft controls the flow of air to the engine [Figure 2- 42] 49 Continental/TCM Fuel- Injection System Fuel/Air Control Unit [Figure 2-42] 50 Continental/TCM Fuel- Fuel/Air Control Unit Injection System air throttle assembly: an aluminum casting which contains: the shaft the butterfly-valve assembly casting bore size tailored to the engine size no venturi or other restriction is used 51  Fuel Control Assembly Continental/TCM parts: – Body made of bronze for best bearing action with the stainless steel valves Fuel-Injection – central bore contains a metering valve at one end and a mixture control valve at the other System end – each stainless steel rotary valve includes a groove which forms a fuel chamber  Fuel Control Assembly Continental/TCM control lever Fuel-Injection mounted on the mixture control valve shaft connected to the cockpit mixture control System Fuel enters the control unit through a strainer Continental/TCM Fuel Control Assembly Fuel-Injection passes to the metering valve [Figure 2-43] System  Fuel Control Assembly Continental/TCM passes to the metering valve [Figure 2-43] this rotary valve has a camshaped edge on the outer part of the end Fuel-Injection face the position of the cam at the fuel delivery port controls the fuel passed to the: System 1.manifold valve 2. nozzles 55  Fuel Control Assembly Continental/TCM returns through the fuel return port connects to the return passage of the center metering plug Fuel-Injection the alignment of the mixture control valve with this passage determines the amount of fuel returned to the fuel pump the fuel flow is properly proportioned to airflow for the correct System fuel/ air ratio by connecting the metering valve to the air throttle 56  Fuel Manifold Valve Continental/TCM Fuel- contains: a fuel inlet Injection System a diaphragm chamber diaphragm spring-loaded operates a valve in the central bore of the body moved by fuel-fuel pressure provides the force for moving the diaphragm enclosed by a cover that retains the diaphragm loading spring fine screen is installed in the diaphragm chamber that all incoming fuel must pass 57 through Continental/TCM Fuel- Fuel Manifold Valve a fuel-injection control valve Injection System – the fuel lines to the cylinders are closed off when the valve is down against the lapped seat in the body which is drilled for passage of fuel from the diaphragm chamber to its base – a ball valve is installed within the valve – fuel is delivered to the fuel manifold valve and provides a central point for dividing fuel flow to the individual cylinders 58 Continental/TCM Fuel- Injection System Fuel Manifold Valve outlet ports for the lines to the individual nozzles [Figure 2-44] 59 Continental/TCM Fuel- Injection System Fuel Manifold Valve outlet ports for the lines to the individual nozzles [Figure 2-44] a plunger valve raised or lowered by a diaphragm to open or close the individual cylinder fuel supply ports simultaneously 60 Continental/TCM Fuel- Injection System Fuel Discharge Nozzle located in the cylinder head outlet directed into the intake port contains a drilled central passage with a counterbore at each end. [Figure 2- 45] 61  Fuel Discharge Nozzle lower end is used as a chamber for fuel/air mixing before the spray leaves the nozzle upper bore contains a removable orifice for calibrating the nozzles Nozzles are calibrated in several ranges, and all nozzles furnished for one engine are of the same range and are identified by a letter stamped on the hex of the nozzle body Drilled radial holes connect the upper counterbore with the outside of the nozzle body Continental/TCM Fuel- Injection System 62  Fuel Discharge Nozzle These holes enter the counterbore above the orifice and draw air through a cylindrical screen fitted over the nozzle body. A shield is press-fitted on the nozzle body and extends over the greater part of the filter screen, leaving an opening near the bottom. This provides both mechanical protection and an abrupt change in the direction of airflow which keeps dirt and foreign material out of the nozzle Continental/TCM Fuel- interior. Injection System 63 The End 64