Engine Selection Parameters - Term Paper Example

Name: Instructor: Course: Date: Introduction Engine Selection Parameters Abstract The research will elaborate on key parameters that are used I the process and procedures during the selection of the superlative engine for the air craft. Thrust To select thrust parameter it starts with sea-lever thrust. Starting trust will always rely on the flow together with the inflow; this is influenced or enhanced by the environment and the type of the propeller. Computations and arithmetic meant for static thrust can be achieved with ease, unlike the theoretical treatment and approach that is very problematical and it can only be made possible by a lower extent of determination and confident computation in the area of the plan point. Due to local flow severance, the performance of propellers under static circumstances can be very responsive with respect to sharp edge angle settings in cooperation with the airfoil shape (John 87).On the other hand an under-sized engine can be over stressed at each of the key throttle point while performing so that the service life will be reduced. Specific Fuel utilization, c /hour: Low specific fuel consumptions is recommended for low operating cost design, if in case any fuel was saved as a result of low sfc, then it possibly can be replaced by profits instituting payload, or basically it can be used to make the operational weight of design low, if the operational weight is low it leads to make the manufacturing cost lower in addition to inferior Direct operational costs. (John 87). In practical applications, other factors are usually highly significant in determining the fuel efficiency of a particular engine design in that particular application. For instance, in aircraft, turbine (jet and turboprop) engines are typically much smaller and lighter than equivalently powerful piston engine designs, both properties reducing the levels of drag on the plane and reducing the amount of power needed to move the aircraft. Therefore, turbines are more efficient for aircraft propulsion than might be indicated by a simplistic look at the table below. Weight: Target of long range designs engine leads to set the target cruise speed to some extent lower than the maximum range speed so this will lower the cruise drag therefore the engine weight will reduce , the more the thrust is low the more smaller and lighter engine will be. Size: Engines size is related to the value of thrust it produces, and if engines fans diameter is increased to produce great amount of thrust then problems of installing an engine under the wing occurs in addition with problem of greater drag. (John 87) .While choosing any possible engine it must be in mind to avoid two major problems that might occur. first one is ground clearance should not be compromised and enough space must be left between an engine and ground for safety reasons while taking off and landing , and secondly cowl drag predictions should be completed to substantiate satisfactory statistics. Engine Design Parameters There are some assured design parameters which affects the engine performance during the flight is in operation and this what leads to affect engines selections parameters mentioned in the sections above and it is important to note these parameters when picking an engine for this project aircraft. The parameter includes: Turbine Entry Temperature (TET): Turbine entry temperature is the point where engine temperature goes to its maximum value, and this temperature has to be under some boundary conditions as the material property of the turbine blades varies. (John, 87) TET can only be increased if thrust per unit air mass flow rate of the engine is increased with minor effect of increasing the sfc. Obviously if additional cooling is used to put the engines temperature down, some minor increase in engine weight will take place. Up to dated engines with the best blades cooling techniques plus using the best materials leaded TET to increase around 1700k as it is found in modern engines. Pressure Ratios (PRbp and PRgg): For any fan engines there is the most favorable link between hot jet velocity and by-pass ratio jet velocity. Pressure of by pass is efficiently linked with pressure of gas generator , increasing the pressure of gas generator tends to a very beneficial effect on reducing the sfc however the values of pressure ratio which is greater than 10 reduce the specific thrust . modern engines have pressure ratios between 35 to 45, again if the engine is needed to contain higher pressures then some negligible weight increase will take place. Bypass Ratio (BPR): The term bypass ratio (BPR)is termed as the ration that is formed between the flow of mass in and the relation of air that is drawn or generated by the fan but on the other hand is by passed or helps in the process of by passing the main engine towards the mass rate passing in between the engine core. In most cases high or great bypass ratios will always attract a lower (actual) exhaust speed. According to research a lower or less bypass ratio will always result into a higher exhaust speed, this will always help in the sustention of higher and supersonic speed or air speed. (John 87)This increases the specific fuel consumption.Jet engines in general need at optimum bypass ratios, the fuel prohibited to move any particular radius is largely independent of airspeed.Increases in BPR beyond about 10 are seen to give very little or no advantage in further reductions in sfc. Why wing mounted engines: In most cases engines that are buried in the direction of the wings root do poses a minimum parasite haul and perhaps minimum mass. Their inboard setting minimizes the yawing instant due to the laid down asymmetric thrust after engine failure. (John 87) However, this structures may pose threats and risks in the common wing models during the event of a blade or also a turbine disk un functionality, It may make it very difficulty or impossible to maintain the so called inlet efficiency, and also it may result into difficulties in the accessibility and maintenance processes. In cases whereby a lager circumference engine is required especially in the current and the latest models of the planes, the entire arm or wing may have to be reassembled. Such principles do eliminate the flap that may be built in the engine exhaust hence minimizing the CLmax. The high temperature, high 'q' exhaust impinging on the flap increases flap loads and weight, and may require titanium (more expensive) structure. The impingement also rises drag, a significant factor in take-off climbs routine after engine stoppage. Eliminating the flap behind the engine reduces CLmax. Engine thrust: To estimate the thrust required for this project aircraft , thrust to weight ratio() is used to calculate amount of thrust needed to fly .Thrust-to-measure is termed as ratio is the ratio of thrust to weight of a jet engine, propeller locomotive. It is a dimensionless quantity and is an indicator of the performance of the engine or the aircraft. To start estimating thrust, this equation below was used: =0.3 Where: T is thrust W is maximum takeoff weight = 2827.551 KN So therefore T = 0.3 x 2827.551 =848.3kilonewtons = 190 705.426 pounds force When looking at the results of thrust to weight ratio it leads to that the aircraft needs an engine selection which produces an 848.3 KN of thrust in total which means each of two engines has to produce an approximate thrust of 424.15 KN. (John 78) To select a perfect engine for the aircraft, it is better to compare from the list of existing engines having same thrust level. The research engine specifications of several engines such as Rolls Royce Trent 895-17, Pratt and Whitney PW4098, General Electric GE90-94B and FJ -33-4 Engine. It is a clear indication that FJ -33-4 engine is the most preferable. Final Engine Choice Comparing the list of engine above and some other existing engines it is seen that FJ -33-4 Engine Is definitely the most influential and proficient commercial transportation engine for this project aircraft. It also has plenty range for thrust development to maintain up with the future standards. Higher Speed and P/P Fan with De-staged Core. Delivering the data in this report cautious, its comparison with other engines clearly shows that it is a class apart from them in terms of thrust and fuel efficiency in addition to that Ge90-94B is today’s long range offering unmatched combination of reliability, low maintenance cost, payload and it can produce enough thrust while using less fuel, (John 78) which make the aircraft able to fly where only four engine plane could fly before. Turbo fans of FJ -33-4 transfer the latest advancements durability, performance and reliability comparing to other engines of the same class. Conclusion In conclusion the fan blades of this engine have been designed using lightest material shaped aerodynamically and to be able to take enough strength. The material used is extremely durable and combined by most advanced aerodynamic profile, it delivers the highest by pass ratio and most thrust acceptable fan in commotional aviation while being the quietest in its class. Not only that this engine is also the cleanest by in cooperating the unique decree redacting system particles entering the fan and centrifuges away from the core, (John 78) providing the purest air supply, that clean air ensures the core that will operate at peak levels by reducer erosion of part profile that could entre performance, with the efficiency of 3-D aerodynamics. The compressor uses 20% fewer parts than other models but still does deliver 19:1 pressure ratio , the ultimate beneficial is that the engine uses 15% less fuel by maintaining the same stall free operations that the other models does. Looking at the all beneficial of the FJ -33-4 it has been finalized to use this engine for the project aircraft. Work Cited John Bourne (C.E.) a treatise on the steam-engine in its various applications to mines, mills, steam navigation, railways, and agriculture: with theoretical investigations respecting the motive power of heat and the proper proportions of steam-engines, elaborate tables of the right dimensions of every part. 9th ed. Longmans, Green 2001. Read More