Question

An Otto engine is operating with natural gas which can be approximated as an ideal gas. Assuming the engine is at standard condition (25°C, 1 atm) before the compression process. Also, temperature of the Otto cycle after the combustion process is 1500 K.

(a) Assuming compression ratio of the Otto engine as 8, 9 and 10, determine the corresponding temperatures of the natural gas-air mixture (natural gas with 100% excess air) after the compression.

(b) Determine the thermal energy release per unit mass of fuel from the combustion process under the above three compression ratios assuming 100% excess air is applied in the combustion.

(c) Determine the net work output per unit mass of fuel from this Otto engine under the three different compression ratios.

(d) Determine the required RPM of the Otto engine (under the three different compression ratios) to provide 80 KW work output rate if the four cylinder Otto engine has a total displacement volume of 2 liter.

Really need the answer for part D

Answer 1

- o-18(652 6g) F 585. 43q R54.83 5o ) RPM of engine , four cylinde Power 8OKww Power- Wetx Cycle Cycle Sec cycle- RPM for a our cylinder engine > RCyoles wi Produce one power igcva Shsok e 2 YEvol utions- 1 power Sboke. ее ラconclusion is, 1G engine rotates NRPM it p'odu ces NAPm Power ycles only Consi st)

we have found Wnet in KT units, we need to convert it into O1 Cycie given total displacement volume Tz compression ratio. בע: 8 Vi 8 BT1

Now, 3 Kg Cycie Power Wnet Cycle PowierWneCgcie Cyla Sec. -Rx80 o 894 N11819 RPM

=y compression rario e9 a) Temparature after compression. Pj 1-4- 04 TE TJ b) Heat in ambu sion : 어18 cs00-114.65) Ner wotk out p otto cycle 3TT4 R98×1500 13-65

561.1 R33 RS Wact 3846 RPM 3 Vp 3 RTJ Whe: R-66 xơ, 328.46 0.8755%5 N 183.5 183 RPM

Assuming compre ssion ratio. :)0 V2 a) Tempaiature atter compiession T3 V2. Pj 14-1 Ta 148.54K b) Heat n combu Stion 0-118 (1500-748.54 = 539.54 K/h R91500 148 54 ng Wne 9s-530.54 - R14-19

A) RPM 3 V2 0ivi RTI - 101 80-0854 xN N183.34 188 RPM