Mindblown: a blog about philosophy.
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CONTINUITY EQUATION
Consider the flow of steam through a nozzle. Let ṁ = steady state mass flow rate of steam, kg/s A = cross-sectional area of nozzle normal to the direction of steam flow at any section, m2 v = specific volume of steam at the same section, m3/kg c = velocity of steam across the section, m/s Then for steady flow…
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INTRODUCTION
The steam nozzle is a passage of varying cross-section by means of which a part of the enthalpy of steam is converted into kinetic energy as the steam expands from a higher pressure to a lower pressure. Therefore, a nozzle is a device designed to increase the velocity of steam. Steam nozzles are of three…
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PERFORMANCE CURVES
Typical performance curves of a reciprocating steam engine under test conditions are shown in Fig. 5.21. Most of the curves are self-explanatory and should be carefully scrutinised for analysis of the variables involved. One salient fact is that the speed curve as shown is practically horizontal with a slight drop as the load is increased, this…
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HEAT BALANCE SHEET
Procedure: For preparing a heat balance sheet for a steam engine cylinder, the engine should be tested over a period of time under conditions of constant load and steam supply. An indicator diagram should be taken and the steam pressure noted at regular intervals of time, an account should also he kept of the steam supply…
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SATURATION CURVE AND MISSING QUANTITY
Saturation Curve: The saturation curve is the curve showing the volume the steam in the cylinder would occupy, during the expansion stroke if the steam is perfectly dry and saturated at all the points. It is plotted on p–V diagram and the wetness of stream can be seen on it at a glance. Figure 5.18 shows a calibrated indicator. The total…
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Example 5.1
The steam supply to a steam engine is at 15 bar dry and saturated. The condenser pressure is 0.4 bar. Calculate the Rankine efficiency of the cycle. Neglect pump work. Solution Given: p1 = 15 bar, p2 = 0.4 bar, x1 = 1.0 From steam tables at 15 bar, h1 = hg = 2789.9 kJ/kg, s1 = sg = 6.4406 kJ/kg.K At 0.4 bar, hf 2 = 317.7 kJ/kg, hfg2 = 2319.2…
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GOVERNING OF STEAM ENGINES
The automatic variation of steam supply with the variation of load is called governing and the device used for this purpose is known as a governor. There are two methods commonly used for steam engine governing. The indicated power vs steam consumption per minute for throttle and cut-off governing are shown in Fig. 5.15. It is obvious from…
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POWER DEVELOPED AND EFFICIENCIES
1 Indicated Power The power developed by the steam engine based on the indicator diagram is the indicated power. Work done by the steam engine per cycle is given by, w = Force × distance travelled by the piston Work done per second is the indicated power where on cover end side. on crank end side. d = diameter…
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MEAN EFFECTIVE PRESSURE
The mean effective pressure is a quantity related to the operation of an internal combustion engine. It is a valuable measure of an engine’s capacity to do work that is independent of engine displacement. 1 Without Clearance The theoretical p-v diagram for a single acting steam engine without clearance is shown in Fig. 5.9(a). It can be obtained…
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ACTUAL INDICATOR DIAGRAM
Indicator diagram is simply a graph between pressure of steam in a cylinder against the steam volume. The following assumptions are made in drawing the theoretical indicator diagram: The theoretical and actual indicator diagrams are shown in Fig. 5.8. The actual indicator diagram is found to be different from the theoretical diagram due to following reason:…
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