What you learn today
- Hydrogen and oxygen in ratio
- Set the mixer
- Check the ratio
Rockets, generators and furnaces need a combustible mixture in the right ratio. Too much oxygen and it burns along unused; too little and hydrogen is left over. According to the game's combustion data 2 mol hydrogen react with 1 mol oxygen to 3 mol steam.
The gas mixer
The gas mixer (StructureGasMixer) has two inputs and one output. Setting is the percentage that comes from input 1, the rest from input 2. At Setting 66.67 two thirds come from input 1.
More precisely: the mixer splits by pressure shares. How many moles that is, however, depends on the temperature – cold gas is denser at the same pressure (p · V = n · R · T). If both inputs have the same temperature, the percentage ratio is also the mole ratio. How much pressure the inlet pipes hold, on the other hand, does not matter.
Setting the mixer
If the temperatures differ, the chip recalculates. With T1 for hydrogen at input 1 and T2 for oxygen at input 2, for 2 : 1:
Setting = 100 · 2 · T1 / (2 · T1 + T2)
mul tmp t1 H2_PARTS
add set tmp t2
div set tmp set
mul set set PERCENTAt equal temperatures 66.67 comes out. If the hydrogen at 250 K is colder than the oxygen at 300 K, it is only 62.5 – the cold gas brings more moles at the same pressure.
Checking the ratio
Calculating is good, measuring is better. A pipe analyzer behind the mixer delivers RatioHydrogen. At 2 : 1 it should be at two thirds. Filling is only allowed while the share is within the band:
sub tmp share TARGET
abs tmp tmp
slt tmp tmp TOLERANCEabs with a fixed tolerance fits better here than sap: the tolerance of sap is relative to the size of the numbers, and for a share you simply want “± 2 percentage points”.
This mixture burns. According to the gas data, hydrogen and methane ignite by themselves from 573.15 K when enough oxidiser is present – a spark does it even earlier. Mixed fuel belongs in pipes and tanks, never in a room with people.
Exercise
Task
Set the gas mixer “Mischer” (hydrogen at input 1, oxygen at input 2) to 2 : 1: Setting = 100 · 2 · T1 / (2 · T1 + T2) with the temperatures of the pipe analyzers “H2Leitung” (T1) and “O2Leitung” (T2). The mixer only runs when both temperatures are there. If RatioHydrogen at the analyzer “Mischung” is at most 0.02 away from 0.6667, “Mischung” lights up and the pump “Abfuellung” runs.
Hints
Hint 1
Numerator: mul tmp t1 H2_PARTS. Denominator: add set tmp t2. Then div set tmp set and times 100.
Hint 2
Both temperatures there? add tmp t1 t2 and snanz ok tmp.
Hint 3
Check: sub, abs, slt with TOLERANCE, then and with ok.
Quiz
5 questions. You pass from 60 % – the server does the grading.
Complete the day
- Passed the simulator exercise
- Passed the quiz with at least 60 %
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