Description : In multi stage compressor, the isothermal compression is achieved by A. Employing intercooler B. By constantly cooling the cylinder C. By running compressor at very slow speed D. By insulating the cylinder
Last Answer : ANSWER : C
Description : In a single stage reciprocating air compressor, the work done on air to compressor is from suction pressure to delivery pressure will be minimum when the compression is A. Isothermal process B. Adiabatic process C. Polytropic process D. Constant pressure process.
Last Answer : ANSWER : A
Description : The clearance volume of the air compressor is kept minimum because A. It allows maximum compression to be achieved B. It greatly affects volumetric efficiency C. It results in minimum work D. It permits isothermal compression
Last Answer : ANSWER : B
Description : Adiabatic compression is one in which A. Temperature during compression remains constant B. No heat leaves or enters the compressor cylinder during compression C. Temperature rise follows a linear relationship D. Work done is maximum.
Description : Dew point can be best defined as the: a. Absolute temperature at which air, upon heating, will evaporate moisture b. . Percentage of moisture that air can hold at a given temperature ... to condense should the temperature drop further e. . Atmospheric pressure at which air will condense moisture
Last Answer : Answer: D
Description : In SI engines knocking can be reduced by (a) Increasing the compression ratio (b) Increasing the cooling water temperature (c) Retarding the spark advance (d) Increasing the inlet air temperature
Last Answer : Ans :c
Description : For a two stage compressor, the ratio of diameter of low pressure cylinder to high pressure cylinder is equal to A. Square of the ratio of final pressure to initial pressure B. The ratio of ... final pressure to initial pressure D. Cube root of the ratio of final pressure to initial pressure
Description : The ratio of indicated power to shaft power of the engine required to drive the compressor is called A. Compressor efficiency B. Volumetric efficiency C. Isothermal efficiency D. Mechanical efficiency
Last Answer : ANSWER : D
Description : If the performance of diesel engine of different sizes, cylinder dimensions and power rating are to be compared, which of the following parameters can be used for such comparison? (a) Swept volume (b) Air fuel ratio (c) Specific brake fuel consumption (d) Volumetric efficiency
Description : In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in A. One stroke B. Two stroke C. Three stroke D. Four stroke
Description : Work input to the air compressor with n as index of compression A. Increases with increase in value of n B. Decrease with increase in value of n C. remains same whatever the value of n D. first increase and then decreases with increase of value of n.
Description : Supercharging is the process of a. supplying the engine with air at a density greater than the density of the surrounding atmosphere b. providing forced cooling air c. injecting excess fuel d. raising the exhaust pressure
Last Answer : ANSWER a. supplying the engine with air at a density greater than the density of the surrounding atmosphere
Description : Which one of the following statements are correct for reciprocating air compressor? A. Its volumetric efficiency increases with increasing clearance ratio B. Its volumetric efficiency increases ... ratio D. Its volumetric efficiency decreases with increasing clearance ratio and pressure ratio
Description : In _____________ injection system only one pump is sufficient for multi-cylinder engine. a) air b) mechanical c) compression fuel d) common rail
Last Answer : Answer: d Explanation: None.
Description : Scavenging air in diesel engine means a. air used for combustion under pressure b. forced air for cooling the cylinder c. burnt air containing products of combustion d. air used for forcing burnt gases out of the engines cylinder during the exhaust stroke
Last Answer : ANSWER d. air used for forcing burnt gases out of the engines cylinder during the exhaust stroke
Description : In a two stage reciprocating air compressor with a suction pressure of 2 bar and delivery pressure of 8 bar the ideal intercooler pressure will be A. 10 bar B. 6 bar C. 4 bar D. 3 bar
Description : In a two stage reciprocating air compressor, the suction and delivery pressure are 1 and 4 bar respectively. For maximum efficiency the intercooler pressure is A. 1.5 bar B. 2 bar C. 2.5 bar D. 3 bar
Description : Explain the necessity of multi-staging and inter cooling in case of two stage compressor with PV diagram
Last Answer : Necessity of multi staging with intercooling in air compression: The large pressure ratio gives rise in high compression ratio and high discharged temperature which produce adverse effect on the efficiency and ... and saving in work and power multi staging with intercooling is necessary.
Description : The coefficient of performance is the ratio of the refrigerant effect to the (a) heat of compression (b) work done by compressor (c) enthalpy increase in compressor (d) all of the above
Last Answer : Ans: d
Description : In vapour compression cycle using NH3 as refrigerant, initial charge is filled at (a) suction of compressor (b) delivery of compressor (c) high pressure side close to receiver (d) low pressure side near receiver
Last Answer : Ans: c
Description : Where does the lowest temperature occur in a vapour compression cycle ? (a) condenser (b) evaporator (c) compressor (d) expansion valve
Last Answer : Ans: b
Description : In vapour compression refrigeration system, refrigerant occurs as liquid between (a) condenser and expansion valve (b) compressor and evaporator (c) expansion valve and evaporator (d) compressor and condenser
Description : The higher temperature in vapour compression cycle occurs at (a) compressor discharge. (b) expansion valve (c) evaporator (d) condenser discharge
Last Answer : Ans: a
Description : In vapour compression cycle the condition off refrigerant is dry saturated vapour (a) after passing through the condenser (b) before passing through the condenser (c)before entering the expansion valve (d) before entering the compressor
Last Answer : Ans: D
Description : The ratio of work done per cycle to the stroke volume of the compressor is known as A. Compressor capacity B. Compression ratio C. Compressor efficiency D. Mean effective pressure
Description : Volumetric efficiency of a compressor without clearance volume A. Increases with increase in compression ratio B. Decreases wit increase in compression ratio C. Not dependent upon compression ratio D. Unpredictable
Description : The capacity of the compressor will be highest when its intake temperature is A. Lowest B. highest C. Atmospheric D. Unpredictable
Description : One of the purposes of sub-cooling the liquid refrigerant is to (a) reduce compressor overheating (b) reduce compressor discharge temperature (c) increase cooling effect (d) ensure that only liquid and not the vapour enters the expansion (throttling) valve
Description : The horizontal line in psychrometric chart joining the change of state of air represents A. humidification B. sensible cooling or heating C. sensible cooling or heating with humidification D. sensible cooling or heating with dehumidification
Description : When, H1 = Total heat of air entering the coil (heating or cooling) H2 = Total heat of air leaving the coil (heating or cooling) H3 = Total heat of air at the end of ... A. cooling and humidification B. cooling and dehumidification C. heating and humidification D. heating and dehumidification
Description : In sensible heating or cooling, A. work done remains constant B. dry bulb temperature or air remains constant C. both of the mentioned D. none of the mentioned
Description : The output of a diesel engine can be increased without increasing the engine speed or size in the following way A. feeding more fuel B. increasing the flywheel size C. heating intake air D. supercharging
Description : The accumulation of carbon in a cylinder results in increase of A. clearance volume B. volumetric efficiency C. ignition time D. effective compression ratio
Description : In compression ignition (CI) engine, the compression ratio is a. Cylinder volume / Clearance volume b. Swept Volume / Cylinder Volume c. Clearance volume / Cylinder volume d. Cylinder volume / Swept volume (Ans:a)
Last Answer : In two stroke engine there is one power stroke in _____ of crankshaft rotation. a. 90° b. 180° c. 270° d. 360° (Ans:d)
Description : Fuel is injected into the cylinder at the end of ______________ stroke. a) suction b) compression c) expansion d) exhaust
Last Answer : Answer: b Explanation: Fuel is injected into the cylinder at the end of compression stroke and not at suction or expansion stroke.
Description : The accumulation of carbon in a cylinder results in increase of a. clearance volume b. volumetric efficiency c. ignition time d. effective compression ratio
Last Answer : ANSWER d. effective compression ratio
Description : In compression ignition engines, swirl denotes a. Haphazard motion of the gases in the cylinder b. Rotary motion of the gases in the cylinder. c. Radial motion of the gases in the cylinder. d. None of the above
Last Answer : ANSWER a. Haphazard motion of the gases in the chamber
Description : What is the formula for compression (rk) ratio of the Otto cycle? a. rk = Volume of cylinder at the beginning of compression / Volume of cylinder at the end of compression b. rk = Volume of cylinder ... c. rk = Volume of cylinder at the end of compression / clearance volume d. none of the above
Last Answer : ANSWER a. rk = Volume of cylinder at the beginning of compression / Volume of cylinder at the end of compression
Description : In a four stage compressor, if the pressure at the first and third stage are 1 bar and 16 bar, then the delivery pressure at the fourth stage will be A. 1 bar B. 16 bar C. 64 bar D. 256 bar
Description : For a multistage compressor, the polytropic efficiency is A. the efficiency of all stages combined together B. the efficiency of one stage C. Constant throughout for all the stages D. a direct consequence of the pressure ratio
Description : Which one of the following is correct? A. In a multistage compressor adiabatic efficiency is less than stage efficiency B. In a multistage turbine adiabatic efficiency is less than the stage ... compressor is greater than one D. Preheat factor does not affect the multistage compressor performance
Description : Which of the following factors increases the tendency of knocking in the CI engines? (a) Increasing both the r and coolant temperatures (b) Increasing both the speed and the injection advance (c) Increasing the speed, injection advance and coolant temperature (d) Increasing the compression ratio
Description : Multistage compression of air as compared to single stage compression offers the advantage of (A) Power saving per unit weight of air delivered (B) Moisture elimination in the inter-stage cooler (C) Increased volumetric efficiency (D) All (A), (B) & (C)
Last Answer : (D) All (A), (B) & (C)
Description : For minimum work input in a two stage compression process the intermediated pressure is the A. Arithmetic process of suction and discharge pressure B. Logarithmic mean of suction and discharge pressure C. Geometric mean of suction and discharge pressure D. Hyperbolic mean of suction and discharge
Description : Multistage compressors are used in industry, because they (A) Reduce the cost of compressor (B) Reduce the size requirement (C) Resemble closely to isothermal compression (D) Are easy to control
Last Answer : (C) Resemble closely to isothermal compression
Description : Classification Of Air Compressor
Last Answer : Air compressors are classified in several different ways, depending on the specific characteristics and features of the compressor. Here are a few common ways that air compressors are classified: ... range of sizes and capacities, from small, portable units to large, industrial-sized compressors.
Description : A reciprocating compressor is not suitable for use as a supercharger because: A. it runs at lower rpm B. the pressure ratio is high C. volumetric efficiency is high D. it is bulky and can handle small quantity of air
Description : The volume of air delivered by the compressor is called A. Free air delivery B. Compressor capacity C. Swept volume D. Mean effective pressure
Description : The maximum delivery pressure in a rotary air compressor is A. 10 bar B. 20 bar C. 30 bar D. 50 bar
Description : The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is A. Less B. More C. Same D. Unpredictable